Plan 9 is a distributed computing environment built at Bell Labs
starting in the late 1980s. The system can be obtained from Bell
Labs at http://plan9.bell-labs.com/plan9 and runs on PCs and a
variety of other platforms. Plan 9 became a convenient platform for
experimenting with new ideas, applications, and services.

Plan 9 from User Space provides many of the ideas, applications,
and services from Plan 9 on Unix-like systems. It runs on FreeBSD
(x86), Linux (x86 and PowerPC), Mac OS X (PowerPC), OpenBSD (x86),
and SunOS (Sparc).
